Athletes commonly use various forms of real and simulated altitude exposure combined with sea level training to enhance sea-level performance. Altitude can be simulated through use of apartments, tents and masks that allow athletes to breathe air containing less oxygen. There is clear evidence that altitude exposure combined with sea-level training enhances endurance performance especially when the altitude is real. It is unclear what the optimum level of altitude and length of exposure is to enhance performance, although researchers generally adopt 3-4 weeks at moderate altitude (~3000m). There is also little evidence to suggest how long the performance effect persists for. Large gains in VO2max have been reported following actual altitude exposure that may be partly mediated via an increase in red cell volume or haemoglobin mass. However, exposure to simulated altitude appears to have a little effect on VO2max probably due to differences in daily exposure time. The effects of altitude exposure on sprint performance are limited to several investigations that demonstrate a tendency for improved performance, especially in repeated sprints.

Expectations from industry and the community ensure that we live in a 24-hour society. Increased demand for flexibility, capital utilisation and competition have initiated or extended shiftwork operations in many industry sectors such as mining, transport, defence, healthcare, manufacturing and security. The most common problems reported by shiftworkers are disturbed sleep and sleepiness. From a biological perspective this is not surprising because shiftworkers are often required to work at times when their mind and body are driven toward sleep. Shiftworkers may therefore be required to attempt sleep during the day; a time at which their mind and body are programmed to be awake and active. When sufficient recovery doesn't occur regularly, sleepiness and fatigue can accumulate. Traditionally, shiftwork and the work-related fatigue that it can create have been 'managed' by limiting the length of shifts and total number of hours worked per week, month or year. However, this approach fails to acknowledge key factors such as the time-of-day of work. Thus, the aim of this thesis is to provide the background, components and preliminary validations of a model to assess hours-of-work and fatigue in a scientifically appropriate manner. / thesis (PhD)--University of South Australia, 1999.

In everyday life memory is commonly used in the completion of future intentions, such as remembering to attend a meeting or remembering to make a purchase at a particular time or place. The ability to remember to complete future intentions plays an important role in older adults maintaining independent living within the community (Cherry & LeCompte, 1999). The studies presented in this thesis evolved out of the lack of current understanding about which component processes involved in remembering future intentions are most susceptible to the effects of aging. In order to investigate these processes, a computer-based analogue of a real-life task was developed (the Virtual Street) that enabled participants to complete a series of intentions (shopping errands) during a simulated visit to a shopping centre. There were two main objectives of this thesis. The first objective was to examine whether the Virtual Street shopping task was appropriate for assessing older and younger adults ability to remember to complete delayed intentions and whether the task had better ecological and face validity than current assessment measures. The second objective was to identify the cognitive processes involved in the task that were vulnerable to the effects of aging, and whether the process of recognising the cues or the memory search of the intention content would be affected. In order to examine these cognitive processes, various factors were manipulated in ways designed to be analogous to real-world situations, which were hypothesized to be sensitive to the effects of aging. These factors include: a change in the location where an intention can be realised (Study 1), the opportunity to learn the intentions (Study 2), the familiarity of the shopping environment (Study 3), and the presence of distractions (Study 4). Overall, the results from the four studies demonstrated that older adults have difficulty remembering delayed intentions, even when the test uses naturalistic stimuli, the tasks are familiar, and they are able to move at their own pace. Furthermore, the results from Study 2 demonstrated that the memory search component but not cue detection was affected in older persons when they were given fewer trials to learn the shopping errands, possibly due to the accessibility of the cue-intention associations may be impaired in older adults. There was no age specific effect on cue detection or memory search in either an unfamiliar street environment (Study 3) or one with increased levels of irrelevant auditory and visual noise (distraction condition, Study 4). In the interruption condition of Study 4, however, cue detection but not memory search was disproportionately affected in older adults after filled interruptions, suggesting that the capacity for self-initiated reinstatement of working memory is reduced in old age. In general, the Virtual Street task was to be a practical means of examining younger and older adults ability to remember to complete delayed intentions. The Virtual Street task also provided an opportunity for behavioural observation of real-life skills and cognitive abilities, within a controlled context. It is hoped that the Virtual Street shopping task will continue to be developed into an ecologically valid measure of assessing older adults memory functioning.

Resistance training is widely prescribed for rehabilitation of injuries and as a method to improve athletic performance. It is accepted that resistance training increases the maximal force production of whole muscle and it has been suggested that the velocity of shortening can increase as well. However, little is known about the effects of resistance training at the cellular level. Therefore, we investigated morphology, force production, velocity, and force-velocity-power relationships of single chemically skinned muscle fibers from chronically resistance trained humans, including cross sectional area (CSA), peak Ca²⁺ -activated force production (P₀), specific tension (P₀/CSA), unloaded shortening velocity (V₀), and isotonic contractions. The untrained group (NT) group consisted of sedentary males (n=6, age =27 ± 2 yrs) while the chronically trained group (CHRT) group consisted of males with 7.7 ± 0.4 yrs resistance training experience (n=6, 22 ± 1 yrs). Maximum voluntary isometric and isokinetic knee extensor strength were measured along with 6 repetition maximum (6RM) free weight bench press and leg press. Muscle biopsies were obtained from the vastus lateralis. Chemically skinned single muscle fibers were mounted between a force transducer and servo-controlled motor and subjected to slack tests to determine peak Ca²⁺ -activated force (P₀) and unloaded shortening velocity (V₀). Isotonic load clamps were used to determine the force-velocity-power relationship. All fiber experiments were performed at 15°C. Fiber myosin heavy chain (MHC) content was determined by gel electrophoresis. The CHRT group was 119% and 81% stronger for 6RM leg press and bench press respectively. Peak isometric torque was 28% greater for the CHRT subjects and was significantly higher at all isokinetic speeds tested. No differences were seen in strength or isokinetic power between groups after normalization for lean body mass. CHRT fibers (n=213) expressing type I, IIa, and I₀a/IIx MHC were significantly greater in CSA (+41%, +51%, and +33%, respectively) and produced significantly greater P₀ (+37%, +48%, and +34%, respectively) than NT fibers (n=236). However, P₀/CSA was not different between CHRT and NT groups. Fibers expressing type IIa/IIx fibers produced greater P₀/CSA than IIa which produced greater P₀/CSA than type I. The P₀/CSA relationship between fibers within groups was type IIa/IIx>IIa>I and was significant for both groups. Fiber V₀ was not different between groups. Absolute power was significantly greater in the CHRT for all fiber types whereas power normalized for fiber volume was not different between groups. This resulted in a significantly greater force at peak power for all but type IIa/IIx fibers and trends for greater velocity at peak power. Single-cell contractile function in terms of V₀ and P₀/CSA, measured under standardized conditions, appears to be unaltered as a result of long term CHRT in young adult males. Group differences in absolute P₀ can be attributed solely to the greater CSA of the CHRT fibers. Long-term CHRT is not associated with a difference in fiber V₀. Therefore, the greater power was due entirely to the greater force. These data suggest that differences in whole muscle strength and power between NT and CHRT groups are primarily due to differences in fiber CSA rather than differences in cross-bridge mechanisms of contraction. Supported by National Institute of Health grant R3AR46392A. / Graduation date: 2002

To examine the potential for exercise to build bone mass during growth, objectives of this dissertation included: 1) determine the effects of 7 months of jumping followed by 7 months of detraining on hip and spine bone mass in the prepubertal children; 2) determine variables that best predict bone mineral content (BMC;g) of the hip and spine in order to develop prediction equations for healthy, Caucasian children, specific to Hologic fan-beam DXA machines; and 3) to examine the potential synergy between calcium intake and the bone response to jump training in prepubertal children. Results/Conclusions Objective 1 (Chapters 2, 3 and 4): children who performed 300 jumps/week at a load magnitude of 8 body weights had significantly greater 7-month changes for BMC at the femoral neck and lumbar spine than controls (4.5% and 3.1%, respectively), and significantly greater 7-month changes for bone area (BA; cm��) at the femoral neck than controls (2.9%). After 7- months of detraining (no box jumping exercises) the jumping group maintained 4% greater BMC and 4% greater BA at the femoral neck than controls. By contrast, at the spine, gains in BMC from the intervention were not retained after an equivalent period of detraining. These data indicate that high-impact jumping enhances growth at the hip. Results/Conclusions Objective 2 (Chapter 5): Age, height, and weight were entered as predictor variables in order to create regression models for healthy, young Caucasian boys and girls. Of these, height and weight independently predicted femoral neck and total hip BMC in both boys (femoral neck: R��=.48, total hip: R��=.63) and girls (femoral neck: R��=.49, total hip R��=.65). Height best predicted spine BMC in boys (R��=.58), but both height and weight independently predicted spine BMC in girls (R��=.54). We report that height and weight not age, best predict bone mineral content at the hip and spine. Results/Conclusions Objective 3 (Chapter 6): Children responded similarly to the jumping program regardless of calcium intake. 73% of our population had dietary intakes of calcium that met the recommended values for their age group. / Graduation date: 2002

Graduation date: 2000

Study Design. This study investigated the effects of a lumbar support belt on lumbar disc deformation and joint angles. Trunk strength and endurance were also compared to disc deformation and joint angles to determine if any meaningful relationships existed. Objective. The purpose of this study was to determine if back support belts relieve stresses encountered by the lumbar spine during lifting activities and thus reduce the risk of injury. Additionally, trunk strength and endurance measures were collected in order to determine if strong, well conditioned trunk musculature aids in the support of the lumbar spine. Summary of Background Data. Low-back pain and injury are responsible for a major portion of lost work days and injury compensation claims. Back support belts have been proposed as a counter measure towards reducing low-back injuries in the industrial setting. Methods. Twelve male subjects (average age, 49.7 years) performed two sessions of stoop type lifting with a loaded milk crate (11.5 kg), at a rate of 4 repetitions per minute, for a total 15 minutes per session in accordance with the NIOSH 1993 lifting equation. The order of testing with and without a belt was randomized for the two sessions. Fluoroscopic images were collected prior to and following both lifting sessions. Fluoroscopic images were collected with the subjects positioned at the initiation (flexed trunk), mid-range, and completion of the lift (erect standing). Images were imported into Auto Cad where lumbar disc deformation and joint angles were measured by calculating changes in position of adjacent vertebra (L3-4 and L4-5). A reduction of deformation was deemed indicative of reduced stress. Trunk extension and flexion strength were measured with a Kin Com isokinetic dynamometer. Trunk flexion endurance was measured via a 60 second curl-up test. Results. Analysis of variance revealed that compressive and shear disc deformation were reduced while in the erect trunk posture for the support belt condition (p<.05). No significant reduction in disc deformation was detected while in flexed trunk postures for the support belt condition (p>.05). A significant inverse relationship was detected (p<05) between: abdominal strength and shear stress (flexed trunk positions), abdominal endurance and shear stress (erect trunk), and spinal erector strength and L4-L5 joint angle (erect trunk). Conclusions. During stoop type lifting, support belts provide a measurable amount of stress reduction of the lumbar spine when the trunk is in the erect posture, with little effect during flexed trunk positions. Strong, well conditioned trunk musculature is associated with reduced stress on the lumbar spine. / Graduation date: 1998

Despite dramatic changes in tennis equipment and technique, more than 30% of recreational tennis players suffer from lateral elbow pain ("tennis elbow"). Certain kinematic and electromyographic characteristics in backhand strokes have been implicated as major factors responsible for lateral elbow pain. From a local tennis club, 22 recreational players who were rated 3.0 to 5.0 skill level (intermediate to advanced) by United States Tennis Association criteria participated in this study. Either one-handed or two-handed backhand ground stroke techniques were used by the subjects according to their preference. Half of the subjects for each technique had lateral elbow pain related to playing tennis. Four groups (one-handed and two-handed technique with and without elbow pain) were analyzed in terms of kinematic and electromyographic characteristics. A three-dimensional kinematic analysis was performed using data obtained with 60 Hz videography. Electromyographic data were collected using a telemetered electromyography (EMG) system at 100 Hz through surface electrodes. / Graduation date: 1997

Graduation date: 1995

Seven men were studied during 30 minutes of leg ergometer cycling at approximately 70% V02 max to determine the effects of caffeine ingestion on the utilization of muscle glycogen. A caffeine solution (250 ml; 5 mg/kg body weight) given one hour prior to exercise (CAF trial), decreased the rate of muscle glycogen depletion by 36 + 11.86% (p. .005) as compared to a decaffeinated control trial. During the CAF treatment, there was a 16% increase in serum FFA prior to exercise. Exercise resulted in a removal of FFA from the blood in both trials. Muscle triglyceride levels prior to exercise in the CAF trial were nearly 23% higher than control levels and suggest, that excess FFA present prior to exercise in the CAF trial were esterified into triglyceride. Subsequent post-exercise values indicated a greater utilization of endogenous lipid. A model based on caffeine's stimulatory effects on muscle lipid mobilization and its inhibitory action on muscle phosphorylase a appears to be responsible for the lessened use of muscle glycogen.